Function parse_json_array_string 

pub fn parse_json_array_string(
    name: &str,
    index: usize,
    array_value: &JsonValue,
) -> Result<String, RpcError>

Parses the element at the specified index in a JsonValue::Array into a string. Returns the string if successful, or an error if the parameter is missing, not an array, or not a valid string.